1. Field of the Invention
The present invention relates to pressure vessels for use with fluid flow meters. More particularly, the present invention relates to hybrid fluid flow meter pressure vessel assemblies that include an interior housing fabricated from plastic, and an exterior ring structure fabricated from metal.
2. Description of Related Art
The pressure vessel of a fluid flow meter, such as a water meter, is typically fabricated from metal, such as bronze. Metal pressure vessels provide desirable benefits relating to, for example: resistance to fluid pressure fluctuations and/or pulsations; resistance to stresses due to in-ground shifting of pipes to which the pressure vessel is connected; and resistance to thread stripping. Metal pressure vessels also advantageously provide a continuous electrical connection for electrical grounding purposes. Many building electrical services are generally grounded through the main cold water line, which is often connected to the metal pressure vessel of a fluid flow meter. Metal pressure vessels, however, have certain disadvantages associated with them relating to, for example: increased weight; high material costs (e.g., copper in the case of bronze or red brasses); increased costs relating to fabrication, such as metal machining; and leaching of metals (e.g., lead in the case of bronze) into the fluid (e.g., potable water) that contacts the interior of the metal pressure vessel.
Pressure vessels for fluid flow meters fabricated from plastic materials are known. See, for example, U.S. Pat. Nos. 4,391,139 and 4,478,440. While addressing some of the disadvantages associated with metal pressure vessels (e.g., reduced weight and minimizing metal leaching into the contacted fluid), plastic pressure vessels typically fail to provide some of the advantages associated with metal pressure vessels. For example, plastic pressure vessels are typically prone to thread stripping, and are prone to failure (e.g., cracking) when exposed to stresses due to in-ground shifting of pipes to which the pressure vessel is connected. In addition, plastic pressure vessels typically do not provide sufficient electrical conductivity for grounding purposes.
It would be desirable to develop new pressure vessels, for use with fluid flow meters, that address the disadvantages associated with metal pressure vessels. It would be further desirable that such newly developed pressure vessels also provide the advantages associated with metal pressure vessels.